... Notice how the region between the two beams of the boom appears to be whited out? This is especially apparent near the top of the boom where the whiting out has caused most of the pulley to be missing. ...
If this is
not an A-frame, then that may represent cables to a cross beam (the dark square in the gap near the top side of the hull?) going around the tip and down the other side, similar to the stays on a mast.
Without
something to control sideways collapse of the boom, and any little swing of the load laterally would likely result in catastrophic failure ... regardless of construction of the stick ...
Enjoy